Do you have other chickens? If so, I'd say leave those batts alone. I know - it sounds cruel and cold hearted, but you don't want to expose your current flock to anything they might be carrying. That's the problem with introducing adult hens from anywhere. You can introduce disease to your flock. I do admire you for wanting to do something kind.

Do you have the means to properly quarantine? Keeping your flocks a minimum of 300' apart, (no free ranging, or they may get next to one or the other's pen), separate feeders and waterers. Changing shoes at the very least, and all your clothes ideally, between one flock and the other. Take care of your existing flock first. I'm sure there's more, this is just what I've read on here. Do an advanced search for medical quarantine. Another thing to consider is one flock or the other may be carriers of disease, while not showing any symptoms themselves. They can still transmit to the other flock.